Pyrotechnic delay device for mild detonating cord



y 23, 1967 J. F. KOWALICK ETAL 3,320,884

PYROTECHNIC DELAY DEVICE FOR MILD DFITONATING CORD Filed July 12, 1966 lit? INVENTORS JAMES F. KOWALICK AT TORNEYS GEORGE); H RE :rR. Y M i United States Patent 3,320,884 PYROTECHNIC DELAY DEVICE FOR MILD DETONATING CQRD James F. Kowaiick, South Hampton, and George F. Hare, Jr., Feasterville, Pa., assignors to the United States of America as represented by the Secretary of the Army Filed Jan. 12, 1966, Ser. No. 520,832 8 Claims. (Cl. 102--27) ABSTRACT OF THE DISCLOSURE A two-piece metallic cylinder housing a pyrotechnic delay train which is actuated through a metal bulkhead by an explosive charge and actuates another explosive charge through another bulkhead, wherein the delay composition is completely isolated from external environmen-' tal factors and from influencing reliability and reducing incompatibility with other parts of the powder trains.

The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to us of any royalty there- The invention relates to a pyrotechnic delay for a mild detonating cord and more particularly to a confined through-bulkhead pyrotechnic delay for a mild detonating cord.

In the past mild detonating cords utilizing through-bulkhead pyrotechnic delays have been found to be inetficient. The problems of incompatibility of the delay composition with other compositions, and unfavorable reactions with the environment have existed as long as delay compositions have been used in powder trains.

With regard to the water absorption problem, the entire powder train was usually sealed from the exterior environment by a sealing wax or other hermetic seal, but the component parts of the powder train were not sealed from each other. Furthermore, when the powder train led into the main charge, an opening or port was left, venting the main charge container. This vented condition remained after the delay functioned, sometimes causing unfavorable results, e.g., side thrust or oblique thrust in a rocket motor.

It is therefore an object of the invention to provide a confined through-bulkhead pyrotechnic delay for mild detonating cord which allows the delay composition to be isolated from the exterior environment, from which it may pick up water and absorb gases.

Another object is the provision of a confined throughbulkhead pyrotechnic delay for mild detonating cord which allows the delay composition to be isolated from other ingredients in the explosive train which might be incompatible with it.

Still another object is to provide a confined throughbulkhead pyrotechnic delay for mild detonating cord which solves the problem of incompatibility of the delay composition with other compositions, and unfavorable reactions with the environment, without sacrificing operability of the delay.

A further object is the provision of a confined throughbulkhead pyrotechnic delay for mild detonating cord wherein delay composition is completely isolated from the external environmental conditions and from other parts of the powder train, thus reducing environmental factors from influencing reliability and reducing incompatibility with other parts of the powder train.

An additional object is to provide a confined throughbulkhead pyrotechnic delay for mild detonating cord wherein the main charge into which the delay train leads is left unvented after delay functioning, thus eliminating any unwanted thrust effect subsequent to delay functionmg.

The above objects as well as others together with the benefits and advantages of the invention will be apparent upon reference to the detailed description set forth below, particularly when taken in conjunction with the drawing annexed hereto.

As seen in the drawings a confined through-bulkhead pyrotechnic delay device 10 consists of two main sections, namely female member 12 and male member 14 which become joined by way of screw threads 16. An appropriate seal 18 of rubber (temporary) or epoxy (permanent) renders the contents of the delay housing 20 independent of environmental moisture and pressure. The members 12 and 14 include mild detonating fuze housings 22 and 24, which are terminated by booster caps 26 and 28, which contain a high explosive 27 and 29 such as RDX, PETN or lead azide. The explosive is inserted in the caps under pressure thereby resulting in a solid mass. The housings 22 and 24 accommodate lead sheathed mild detonating cords 31 and 33 (shown in dotted lines) which contain l2 grains per foot of RDX or PETN 35 and 37, and terminates up against the high explosive charges in the external booster caps 26 and 28. Cords 31 and 33 are covered with fabric 30 and 32 as they extend beyond the housings 22 and 24. The terminal booster assemblies (22, 26, 30, 31 and 24, 28, 32 and 33) are each integral and can easily be removed from or inserted into the members 12 and 14 by simply manipulating the lock nuts 34 and 36 which screw, by way of threads 38 and 40, onto the members 12 and 14.

Located in male member 14 is the delay housing 20 which includes two internal booster caps 42 and 44 each containing similar quantities of the same high explosives r as are contained in the two booster caps 26 and 28 with the exception that the high explosives in the booster caps 42 and 44 are topped off with equal charges of a primary explosive 41 and 43, such as lead azide, which is also inserted in the solid state. In each case, the booster caps 42 and 44 are completely filled with high explosive.

The booster caps 42 and 44 terminate in two metallic cups 46 and 48 which are axially vented in their sidewalls at 50 and 52 and which are housed in two larger metallic cups 54 and 56, which are, in turn, housed in cavity 58. The purpose of the empty cup is to soften the explosive effect thereby preventing blow through. Adjacent to the cups 46 and 48 are charges of an igniter mixture 60 and 62 also in the solid state which are vented as at 64, 66, 68, and 70 towards the walls of metallic cylinder 72, which is located between cups 54 and 56 and which contains a conventional delay composition 78 which is also in the solid state. Webs 74 and 76 of specific thickness exist between the booster caps 26, 42 and 28, 44.

In operation the mild detonating fuze cord 32 is initiated at some point in an overall electro-mechanical explosive system. The point of initiation being several inches or more away from the juncture of fabric covered cord 32 with the terminal booster 24. Initiation proceeds along the cord 32 at detonation velocities to the termination point in the booster cap 28, whereupon the high explosive charge therein is initiated by the energy input from the cord 33. During initiation and reaction of the high explosive in the booster cap 28, shock waves are transmitted throughout member 14, causing sufiicient energy to be received by the high explosive in the booster cap 44. This reaction causes initiation of the high explosives in the booster cap 44 thereby causing heat and mass transfer to occur through the vent 52 in cup 48. The igniter mixture 62, receives adequate energy to ignite and vent hot gases through the vent holes 68 and 70 where the gases ignite the delay composition 78 in the cylinder 72. The delay composition 78 reacts at a linear rate to effect a predetermined time delay, whereupon it ignites the igniter mixture 60 through vent holes 64 and 66. The igniter mixture 60 reacts to form hot gases which are vented through the vent hole 50 in cup 46 to ignite the lead azide or other primary explosive top off charge in booster cap 42. Upon initiation, the primary high explosive top off charge initiates any high explosive charge in booster cap 42. The combined effect of this high explosive initiation is to initiate the high explosive in booster cap 26 in a through-bulkhead manner. Initiation of the high explosive in booster cap 26, in turn, initiates the adjacent mild detonating fuze cord 31 by way of the explosive carried by terminal booster 22.

This functioning as described could have occurred in a similar fashion starting with cord 30 and as such this device actually is a two-way system.

The metallic portions of the device, namely parts 12, 14, 22, 24, 2s, 2s, 34, 36, 42, 44, 46, 4s, 54, 56, and 72 can be aluminum, brass, steel, ceramic, etc.

The igniter mixtures 60 and 62 can be any gaseous ig-' niter mixture capable of igniting a corresponding delay composition 78 in the fashion described. All explosive compositions should be compatible with the metallic com positions.

Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

We claim:

1. A pyrotechnic delay comprising a male member and a female member, said male member including a mild detonating fuze housing, said housing terminating at a first end in an external booster cap, and at a second end in a mild detonating cord having a fabric covering, said female member being threaded to receive said male member, said female member including a mild detonating fuze housing, said housing terminating at a first end in an external booster cap and at a second end in a mild detonat- '4 ing cord having a fabric covering, said male member being threaded to be inserted inside of said female member, a seal between said male and female members, a delay housing provided in said male member, said delay housing separated from said external booster caps by webs, said delay housing including a metallic cylinder, a large metallic cup, having a plurality of vent holes therein, located on either side of said cylinder, said large metallic cups having smaller metallic cups therein, said smaller metallic cups having vent holes therein, and an internal booster cap located in each smaller metallic cup.

2. A delay of the type described in claim 1, wherein said metallic cylinder contains a delay composition.

3. A delay of the type described in claim 2, wherein said large metallic cups contain charges of igniter mixture.

4. A delay of the type described in claim 3, wherein said delay housing booster caps contain a high explosive and a primary high explosive.

5. A delay of the type described in claim 4, wherein said booster caps located at the ends of said mild detonating fuze terminal boosters contain a high explosive.

6. A delay of the type described in claim 5, wherein said mild detonating fuze terminal boosters have a center core which is filled with explosive.

7. A delay of the type described in claim 6, including lock nuts to secure said mild detonation fuze housing to said mild detonating cords.

8. A delay of the type described in claim 7, wherein said lock nuts are screw threaded to said male and female members.

References Cited by the Examiner UNITED STATES PATENTS 4/1964 Schnepfe 1027O X 3/1966 Allen 10270 

1. A PYROTECHNIC DELAY COMPRISING A MALE MEMBER AND A FEMALE MEMBER, SAID MALE MEMBER INCLUDING A MILD DETONATING FUZE HOUSING, SAID HOUSING TERMINATING AT A FIRST END IF AN EXTERNAL BOOSTER CAP, AND AT A SECOND END IN A MILD DETONATING CORD HAVING A FABRIC COVERING, SAID FEMALE MEMBER BEING THREADED TO RECEIVE SAID MALE MEMBER, SAID FEMALE MEMBER INCLUDING A MILD DETONATING FUZE HOUSING, SAID HOUSING TERMINATING AT A FIRST END IN AN EXTERNAL BOOSTER CAP AND AT A SECOND END IN A MILD DETONATING CORD HAVING A FABRIC COVERING, SAID MALE MEMBER BEING THREADED TO BE INSERTED INSIDE OF SAID FEMALE MEMBER, A SEAL BETWEEN SAID MALE AND FEMALE MEMBERS, A DELAY HOUSING PROVIDED IN SAID MALE MEMBER, SAID DELAY 